Coating method and apparatus

ABSTRACT

THERE IS DISCLOSED A METHOD AND AN APPARATUS FOR APPLYING A COATING MATERIAL, SUCH AS CHROMIUM TO A SUBSTRATE, SUCH AS A RAZOR BLADE. THE METHOD PREFERABLY UTILIZERS A DRUM UNIT HAING A PLURALITY OF DRIVE HUB ASSEMBLIES, EACH OF WHICH SUPPORTS CARRIER MEANS FOR CARRYING A LARGE NUMBER OF RAZOR BLAKDES AND IN WHICH THE HUBS ARE DRIVEN, FOR EXAMPLE, BY AN EPICYCLIC GEAR OR CHAIN MECHANISM, SO AS TO EXPOSE DESIRED PORTIONS OF THE BLADES, IN A DESIRED TIMED RELATION, TO THE COATING MATERIAL WHICH CAUSED TO EMANATE FROM A FIXED SOURCE. THE SOURCE COMPRISES A SOCALLED SPUTTERING MODULE INCLUDING A HOUSING HAVING, AT THE TOP PART THEREOF, A PAIR OF ANGLED TARGET PLATES FROM WHICH THE COATING MATERIAL IS TAKNE, AND THE BOTTOM THEREOF, AN OPENING PAST WHICH THE CARRIERS ARE MOVED BY THE DRUM. THE COATING MATERIAL IS REMOVED FROM THE TARGET PLATES AND DEPOSITED ON THE BLADES BY A SO-CALLED &#34;RF SPUTTERING,&#34; PROCESS. IN THIS PROCESS, WITH THE APPARATUS AND MATERIALS IN A VERY HIGH VACUUM, A HIGH RADIO FREQUENCY (R.F.) IS IMPRESSED ACROSS TWO ELECTRODE PLATES, EACH OF WHICH IS DISPOSED IMMEDIATELY BEHIND THE TARGET PLATES. THEREAFTER, A NORMALLY INERT GAS SUCH AS ARGON IS INTRODUCED INTO THE AREA BETWEEN THE PLATES AND IONIZED BY BOMBARDMENT WITH A HIGH VELOCITY ELECRONS. THE RESULTING POSITIVE IONS IN THE GLOW DISCHARGE ARE THEN ACCELERATED AND STRIKE THE TARGET PLATES EJECTING OR &#34;SPUTTERING&#34; SUBSTANTIALLY ELECTRICALLY NEUTRAL PARTICLES OF COATING MATERIAL THEREFROM, WHICH ARE THEN DEPOSITED ON THE EXPOSED SURFACES OF THE SUBSTRATE AND FIRMLY ADHERE THEREON TO FORM A COATING OF EXTREME SMOOTHNESS AND ADHESION.

Jan. 4,:1972 -r5 ETAL 3,632,494

COATING METHOD AND APPARATUS Filed Nov. 6. 1967 6 Sheets-Sheet l 4 I I56 T I? 2 2 I58 v 40 v l: I J] W x 26 26 Hlllll 5 g INVENTORS l l REA/ce F Ham re; FRANK R. K4051,

66-02456 14: a1 J2me; R SK/NM-R Jan. 4, 1972 L. F. HERTE ETAL 3,632,494

COATING METHOD AND APPARATUS Filed Nov. 6, 1967 6 Sheets-Sheet 2 IN VEN TOFI'S LAw/eewce-FJ eer/%4-z R 1 05;,

660656 C. LAME, :3 3/1/15 IPSK/NA/E 1972 L. F. HERTE ETAL COATING METHOD AND APPARATUS 6 Sheets-Sheet 3 Filed Nov. 6, 1967 INVEN TORS LAwka/(E .F flaerf @AX/KE. (4.0 Sr,

Jan. 4, 1972 -r5 ET AL 3,632,494

COATING METHOD AND APPARATUS Filed Nov. 6, 1967 6 Sheets-Sheet 4 88 84 M 1; 74 l i u ,/92 H I06 94 A I INERT GAS INVENTORS [A WREA/C FHc-te T6; eM/z B 1 4 05$,

L. F. HERTE ETAL 3,632,494

COATING METHOD AND APPARATUS 6 Sheets-Sheet 5 Jan. 4, T 1972 Filed Nov. 6, 1967 E .3 wow ,INVENTORS fkAA/K ,ek wss lnwkcure'Flle-ere,

6w; 6 [AN5 51 55/16 R'Sk/m/e-e Jan. 4, 1972 F, HERTE ErAL 3,632,494

COATING METHOD AND APPARATUS Filed Nov. 6, 1967 6 SheetsSheet 6 29s 292 gag I 318 1 zzovAc g} TDI l .05 m s 2 5 302| DOK Pig}? 50s I ace-3m POWER ON IOFF INVENTORS LAwRe'AEF/ FZTG] EAL K Rho United States atent COATING METHOD AND APPARATUS Lawrence F. Herte, Palo Alto, and Frank F. Kloss, San Francisco, Calif., George C. Lane, Milford, Conn., and James R. Skinner, Cnpertino, Calif., assignors to Warner-Lambert Company, Morris Plains, NJ.

Filed Nov. 6, 1967, Ser. No. 680,926 Int. Cl. C23c /00 US. Cl. 204-192 13 Claims ABSTRACT OF THE DISCLOSURE There is disclosed a method and an apparatus for applying a coating material, such as chromium to a substrate, such as a razor blade. The method preferably utilizes a drum unit having a plurality of driven hub assemblies, each of which supports carrier means for carrying a large number of razor blades and in which the hubs are driven, for example, by an epicyclic gear or chain mechanism, so as to expose desired portions of the blades, in a desired timed relation, to the coating material which caused to emanate from a fixed source. The source comprises a socalled sputtering module including a housing having, at the top part thereof, a pair of angled target plates from which the coating material is taken, and the bottom thereof, an opening past which the carriers are moved by the drum.

The coating material is removed from the target plates and deposited on the blades by a so-called RF Sputtering, process. In this process, with the apparatus and materials in a very high vacuum, a high radio frequency (RF) is impressed across two electrode plates, each of which is disposed immediately behind the target plates. Thereafter, a normally inert gas such as argon is introduced into the area between the plates and ionized by bombardment with high velocity electrons. The resulting positive ions in the glow discharge are then accelerated and strike the target plates ejecting or sputtering substantially electrically neutral particles of coating material therefrom, which are then deposited on the exposed surfaces of the substrate and firmly adhere thereon to form a coating of extreme smoothness and adhesion.

BACKGROUND OF THE INVENTION (1) Field of the invention Generally, the present invention relates to a novel method and apparatus for surface coating of articles.

More particularly the field of the invention is that of coating a substrate by a process of metal transfer called cathodic sputtering. In this process, the principal elements are an article or substrate to be coated, a coating material, a target material, a target plate for holding the coating material, electrode plates for causing positive ion in a glow discharge to strike the target plate to eject the coating material, means to control the deposition of the coating and means for carrying the article to be coated and for exposing the desired portions thereof to the coating material.

The principal differences between the instant method and early sputtering are that the coating or target material need not be metallic, may be attached to rather than an intergal part of the cathode, and is of greatly improved efiiciency in regard to rate and accuracy of deposition, operating temperature and in many other regards which are referred to further herein.

The method of the invention is desirably carried out by placing the electrode plates in a very high vacuum to form a peak or apex, with the upper edges thereof adjacent each other, and the lower edges more widely spaced apart and with an opening therebetween at the lower edges, placing the target plates immediately adjacent the inner surface of the electrode plates, impressing a high frequency alternating current on the plates, causing electron flow therebetween and development of a high negative charge thereon, and leaking argon or like gas into the inter-electrode space. Thereupon, the electrons bombard the argon, ionizing it, and the positive ions thus produced are attracted to the target plates by the negative charge on the electrode plates. The positive ions strike the target with such momentum that atoms or molecules from the target are sputtered from the target, and are deposited on the article or substrate. Another aspect of the invention relates to the provision of a mechanism for holding the desired article or substrate, in this case, a plurality of razor blades, so that they may be passed in a controlled manner beneath the target plates containing the coating material. This mechanism may be generally described as a drum which is adapted to support a plurality of hubs which in turn support carrier means on which razor blades are removably mounted for coating. The drum and hubs are driven by means of an epicyclic gear or chain mechanism so that they rotate in a desired rimmed relation about two axes so as to expose the desired surface thereof to the opening beneath the target plates at particular angles to present those portions of the blades it is desired to coat to the target plates.

(2) Description of the prior art In general, the prior art methods of coating particular substrates with various materials, particularly thin metallic films, has been accomplished by vacuum deposition, generally classified as evaporation, according to the following generally known methods.

A first method was an ordinary evaporation of a metal coating from a hot filament, wherein the filament was heated and the metal attached thereto was merely evaporated in the vacuum away from the filament along relatively straight lines in all directions, coating whatever object lay in their path. For example, in the art of electron microscopy, it is known to shadow a substrate by evaporating gold or other low boiling point metal onto a specimen in order to create solid phase or permanent shadows which would be easily visible under a microscope.

An improvement in the ordinary evaporation method was the so-called electron beam deposition whereby the coating material was held in one location and an electron beam was directed at the coating material, the beam being formed and maintained by the application of a magnetic field to an electron source. A heated filament was used in this method.

Another known method is so-called diode sputtering, wherein high energy electrons strike and ionize atoms of an inert gas such as argon, and the ionized particles or plasma thus formed strike a target containing the coating. The target surface sputters ofi coating atoms, which are deposited on the substrate. A method such as this is a considerable improvement over several known methods, but the relatively large amount of ionized gas creates an arc effect and gives off considerable heat, even though this method has the advantages of somewhat improved uniformity and good adhesion of the coating material to the substrate. Another, more modern method, is so-called triode sputtering, wherein a first electrode is rendered positive and electrons from a hot cathode are accelerated to the electrode while ionizing an inert gas, such as argon. The positive ions thereby attained are accelerated to a second negative charged electrode containing the target material. When the ions strike the target material is sputtered to the substrate which was desired to be coated. Although this method of coating possesses number of advantages, it is not commercially preferable for coating many types of substrates which are adversily affected by contamination resulting from particles evaporated from the hot cathode.

All of the foregoing known methods of deposition of thin films have been considered, but none were found to be commercially desirable for coating substrates having extremely fine cutting edges. Some of the purposes for which coating is desired will now be discussed.

It has always been desired, in the razor blade art, to form a very sharp blade edge suitable for shaving, and to have that edge combine the advantages of corrosion resistance and longevity, as well as presenting a smooth and lubricous surface to the face of a shaver. Thus, it is desired to have a relatively corrosion-resistant blade having an extremely hard or tough material which would resist dulling. Thus, an ideal razor blade would combine the advantages of a long life in use as well as long shelf life, combined with an extremely sharp cutting edge and maximum smoothness for purposes of shaving comfort.

In the razor blade art, it is well known in the interest of shaving comfort, to coat a portion of the blade adjacent the cutting edge with a lubricous plastic. such as a fluorocarbon polymer, for example, polytetrafluoroethylene or the like. Likewise, in the last several years, razor blades made from harder and tougher materials than those previously used have come into common use and have been accepted on a large scale commercially. Thus, the use of stainless steel for making razor blade is now quite common. However, it is likewise known that stainless steel is not the perfect material for making an ideal razor blade, but one which at present best combines the advantages of acceptable competitive cost, corrosion resistance and durability of the shaving edge imparted thereto. However, even in spite of great commercial success of the stainless steel blade, there has been a demand in the razor blade art for a razor blade which would harmonize, at reasonable cost, the seemingly contradictory requirements of using a very hard, tough metal substrate for securing a long wearing blade edge, and using metals, which although sufiiciently hard and tough to last for a long time, may nonetheless be readily ground to an extremely fine sharp edge, free from brittleness and microscopically jagged edges or voids in the sharpened surface.

Thus, a greatly improved razor blade would be one in which the blade could be manufactured from conventional materials, such as ordinary steel or stainless steel, and could then be given a very fine smooth metal surface, coating, which would not require further finishing of the coating metal to impart there characteristics to the edge. However, since no known materials combine these advantages, a great deal of effort has been placed on developing methods and apparatus for coating blade edge of existing type razor blades. However, metal coating already sharpened blade edges by conventional methods has always resulted in an edge which requires further finishing, and the application of a hard coating, such as chromium, has resulted in a blade which was very brittle near the edge portions, and which was very diflicult to grind down or polish to the desired degree of smoothness, especially at a reasonable cost.

Thus, there has been a great demand for a simple and economical method of placing a fine, hard, extremely smooth coating on a finished razor blade edge portion which would not require further treatment, but which would impart to such a blade edge the desirable characteristics of smoothness and hardness as well as corrosion resistance.

The invention of the applicants, namely, the method of coating the blade edge by means of radio frequency sputtering and the developing of an apparatus for carry ing out this method, accomplished its objects to provide a method and apparatus for improved surface coating of razor blades and like substrates.

4 SUMMARY OF THE INVENTION In view of the shortcomings of prior art methods and apparatus for coating razor blades, it is an object of the invention to provide an improved method and apparatus for placing a very thin, very fine coating on a sharpened metal surface after sharpening such a surface, to provide an improved blade or the like.

A further object of the present invention is to provide a method of coating a desired substrate with a desired coating material at low temperatures and at a reasonable cost, and to attain an extremely uniform coating which needs no further treatment to present a sharp cutting edge to the user.

Another object is to provide an apparatus for carrying out radio frequency sputtering of a metal coating material onto a razor blade.

Still another object of the invention is to provide an apparatus for supporting a series of razor blade holders and moving the holders in such a way as to expose blades carried thereon to the plasma sputtering module so that the desired portions of each blade may be given a uniform coating in the desired location.

A still further object is to provide a coating apparatus which is simple and compact to facilitate ready inclusion and use thereof in a high vacuum chamber.

The present invention achieves its objects and overcomes the disadvantages of the prior art, by providing a method which includes the steps of providing a sputtering module which includes two fiat electrode plates arranged to form a peak at one end thereof and an opening opposite the peak, placing target plates containing the coating material in front of the electrode plates, providing carrier means for supporting a plurality of articles to be coated, drawing a very high vacuum in the area surrounding the sputtering module and the carrier means, impressing a radio frequency current across the electrode plates, leaking an inert gas into the region between the plate and passing the articles to be coated across the opening between the peaked plates so that electron bombardment of the gas ionizes the gas, the ions strike the target plates, sputtering the coating material therefrom, and the articles are uniformly coated by the sputtered material.

The method is advantageously performed by an apparatus which includes a drum or like means for carrying a plurality of article holders past the sputtering module, and exposing a desired portion of the blades or other articles held on the carrier to the opening in the sputtering module in a timed relation so as to obtain a coating of desired uniformity, thickness and adhesion to the article. A preferred embodiment includes a drum holding a plurality of rotating hubs, and an epicyclic drive mechanism for rotating each of the article carriers into a desired location as each hub unit passes the sputtering module, by utilizing relative rotation of the drum and hub assemblies.

Other and further objects and advantages of the present invention, including the manner of attainment thereof, will become more apparent when considered in conjunction with a description of the preferred embodiments of the invention described further herein and shown in the drawings, in which corresponding reference characters denote like parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. I is a front view, partly in elevation and partly n section, showing the coating apparatus of the present invention;

FIG. 2 is a side view, partly in section and partly in elevation, and with portions broken away, showing the coating apparatus of the present invention.

FIG. 3 is a rear view, partly schematic, showing a portion of the coating apparatus of the present invention;

FIG. 4 is a top view, partly in plan and partly in section, showing the coating unit of the present invention;

FIG. is an enlarged sectional view, of the blade carrier unit shown in FIG. 4.

FIG. 6 is a schematic view of a combination radio frequency generator and impedance matching network unit which may be used with the present invention;

FIG. 7 is a schematic drawing of a power supply unit for powering certain components of the combination unit shown in FIG. 6;

FIG. 8 is a schematic drawing of a power supply unit for energizing other portions of the unit shown in FIG. 6.

Referring now to the drawings in greater detail, FIG. 1 shows an outer vacuum chamber 20 including a top wall portion 22, side wall portions 24 and a base portion 26, all of said portions cooperating to form the chamber 20 which is capable of maintaining an extremely high vacuum therein, such as will be discussed in greater detail presently. The chamber 20 is shown as being made from metal, but it is understood that it may be made of glass or other like material known in the high vacuum art as being suitable for making such chambers. In the event glass were used, the shape of the chamber so would be that of a bell jar. If a frangible material, such as glass is used, an implosion shield (not shown) may be fitted, as is well known in the high vacuum art.

Contained inside the vacuum chamber 20 are the two principal components of the coating apparatus of the present invention, namely the carrying means 28 for supporting a number of razor blades or like articles to be coated, and a sputtering module 30, in which is disposed the coating material which is to be placed onto the blades or other articles carried by the carrying means 28.

Referring now to the carrying means, FIGS. 1 and 2 show that the means 28 includes a stand assembly 32 which contains a front leg member 34 and a rear leg member 36, each of which includes feet 38 which are adapted to be fastened to a portion of the base 26 of the vacuum chamber by fastening means in the form of cap screws 40 or the like. Mounted on the stand 32 is a drum assembly 42 which comprises a front plate 44, a rear plate 46, a central axle shaft 48, and drive means in the form of a crank unit 50 or the like.

In this embodiment, O-ring or like air-tight seal means 52 are provided for attaching an inner end portion of the bellows 54 to the side wall 24 of the housing chamber 20. The bellows 54 includes a cylindrical extension portion 56 thereon, so that, as is shown in FIG. 2, rotation of the shaft 48 and the drum 42 mounted thereon may be accomplished without the need for a seal which contacts rotary parts, as long as the bellows 54 is sufiiciently flexible to allow the knob 58 or other means mounted on the end of the shaft 48 to rotate and describe a circle about the axis of the shaft 48. Referring again to the carrier means 28, it may be seen that a cylindrical shell 60 connects the front and rear plates 44, 46 of the drum 42, and that a plurality openings 62 are provided so that the interior of the drum assembly 42 will be rapidly and completely evacuated when a vacuum is drawn on the vacuum chamber 20.

Referring now to FIGS, 4 and 5, it can be seen that the rear wall 46 of the drum 42 is adapted to carry a series of relatively rotatable hubs 64, and that these hubs 64 are carried by inner bean'ng races 66 on which balls 68 rotate, inside outer races 70. FIGS. 4 and 5, also show that the hubs 64 contain drive means in the form of chain sprockets 72 disposed on the outer portions thereof, and that the sprockets 72 are fastened as by keys 74, to the body of the hub 64. In addition each hub contains locking means in form of a ball 76 driven by a spring 78 exerting an inwardly directed force thereon, as well as a plurality of notches 80 in the inwardly directed faces 82 of the hub 64.

Referring again particularly to FIGS. 4 and 5, it will be seen that each hub 64 is adapted to receive blade carrying means in the form of a bayonet unit 84, which will now be described.

The blade carrying means or bayonet unit 84 comprises a front locking bar 86, a rear locking body 88, joined together by a center guide member 90, and on either side by left hand and right hand guide members 92, 94. Each of the guide members 92, 94 has a stub extension 96 adapted to be received in the recesses in the front face 82 of the hubs 64, as previously set forth.

The front locking bar 86 is removably attached to the guide members 90, 92, 94 and in use a plurality of blades B or other articles to be coated are placed on the guide members 90, 92, 94, and the front locking member 86 is then placed on the end of the members, and pushed finger tight to compress the blades B against each other into a relatively tightly abutting relationship. Locking springs clips 98 are provided for holding the bar 86 in place. An extension 100 of the center guide member 90 is provided for receiving handle means in the form of a knob 102 thereover so that manipulation of the bayonet 84 is facilitated. iExtending outwardly from the rear locking bar 88, is central support means in the form of a nose unit having an annular circumferential groove 106 therein, whereby the locking ball 76 under the influence of the spring 78 may be urged in the groove 106, holding the nose 104 and the blade carrying means 84 associated therewith in the desired locked relation with the hub unit 64 The locking ball 76 and spring tension thereon are desirably adjusted so that a moderate hand pull will remove the blade carrying means 84, but also so that the bayonet 84 will remain locked in position as shown in FIG, 5 unless pulled outwardly therefrom.

The diameter of the nose 104 is such that it will fit relatively snugly into the hub assembly 64 so that the entire bayonet 84 may be cantilevered outwardly of the hub 64. It is preferred that the knob 102 is integrally formed with, and fastened to, the front locking bar 86 so that the two may be removed and replaced or manipulated as a unit. It is also to be noted that the provision of the key 74 insures that the sprocket or the like drive means 72 will rotate with the hub 64, for reasons which will appear more fully herein.

Referring now to FIG. 3, it may be seen that, whereas each hub 64 carries an associated individual drive means 72 therewith, a chain unit 108 is provided which engages the radially outermost edges of each of the plurality of sprockets 72, and, in between one pair of gears 72, the chain 108 extends inwardly toward the center of the drum member where it is trained around a stationary sprocket 110, which is held fixed in relation to the stand 32. A tension control means 112 is provided in the form of an idler gear 114 which is mounted on a pivoted plate 116 which pivots about a point in the form of a cap screw 118, through the are permitted by the cutout 120. When the desired position of the idler gear 114 is reached the locking screw 122 is tightened and the idler is held in a position placing the desired amount of tension on the chain 108.

In a preferred embodiment, it desired to align the blade carrying means or bayonet units 84 so that a blade thereon will present a cutting edge thereof parallel with the top surface of the drum and directly under the sputtering module 30, and, upon rotation of the drum member through one cycle, will present the opposite face thereof to the opening beneath the sputtering module 30. Therefore, it is preferred that the stationary sprocket contains a fixed number of teeth, say, for example, 24, and that each outer or planetary gear 72 will contain two times the number of teeth possessed by the stationary gear or sprocket 110, that is, 48 teeth in the example just referred to. In this manner, when each individual carrying means or bayonet 84 is presented to the opening in the sputtering module 30, alternate top and bottom faces of blades carried thereon are presented in succession, Although it is not strictly necessary, in

7 accordance with the present invention to use a chain driving means, the use of a chain is simplier and less expensive, and provides for a generally more desirable layout than other driving means, such as gears or the like, and is more economical.

Thus it will be seen that the carrying means for the blades or the other articles to receive the desired coating generally comprises a drum means held on a suit able stand and constructed and arranged so that rotation of the drum itself serves to rotate the bayonet members held on the hubs so that alternate top and bottom for example, of the articles held are presented to the sputtering module as described above.

Referring now to a second principal component of the invention, sputtering module 30 is supported in place by a ground shield cylinder 124 which is held by support means in the form of an arm 126 adjustably fastened, to permit adjustment of target to substrate distance, to a rigid vertically disposed conduit column 128, which in turn is fastened to a frame assembly 130 in the base 26 of the housing chamber 20. Immediately beneath the ground shield cylinder 124 is a holder unit 132 which supports left hand and right hand ground shield members 134, 136, to which are attached end walls 138, 140, the front end wall having a viewing window 142 disposed therein. The inside of the sputtering module 30 contains identical left and right hand electrode plates 144, which are supported by fasteners 146 holding insulators 148 to insulate the electrode plates 144 from contact with the ground shields 134, 136. Current is supplied to the electrode plates 144 by means of lead means 150. In the preferred construction, the lead means 150 are in the form of hollow copper tubes which are brazed, soldered, or otherwise securely electrically and mechanically fastened to the electrode plates 144. The copper tubes 150 serve as combination electric leads and coolant conduits, inasmuch as each hollow copper tube is adapted to circulate water on the inside thereof, and to carry the radio frequency charges to the plates 144, around the exterior of the tubes or leads 150. Target plates 152 are disposed on the inner edges respectively of the electrode plates 144, and may be fastened thereto by any suitable means, preferably means which facilitate removal and replacement of the target plates 152, such as spring clips or the like, illustration of which is omitted for the purpose of clarity.

Referring now particularly to FIG. 1, it will be understood that the complete right hand electrode plate 144 and carrying means therefor, as well as the right hand target plate 152 are shown, but it will be further understood that the left hand plate which is only fragmentarily shown on the other side of the module 30, is identical to the right hand plate 144 and is held in place by the left hand ground shield 134. Together, the two plates 144, when disposed within the ground shield 134, 136, as shown, form what is referred to herein as a peak, which has such geometry in order to facilitate the flow of electrons between the two plates, as well for purposes of leaving an opening therebetween for the passage of the articles to be coated. It is not strictly necessary, in accordance with the present invention that the peak be of the exact configuration shown, or that the opening being disposed at the bottom thereof, but such construction has proved most efiicient, and accordingly is preferred in keeping with the present invention.

Referring again to the FIG. 1, it will be noted that a large sheathed cable means 154 or the like is shown surmounting the ground shield cylinder 124, and this sheath 154 carries a coaxial cable means inside thereof (FIG. 4), from which the leads 150 extend to the electrode plates 144. The sheathed or armored cable 154 then extends downwardly through the column 128 and thence outwardly of the vacuum chamber to the radio frequency generator unit and impedance matching network which will be described further herein.

Referring now to FIG. 2, it will be seen that the locations of an oil diffusion pump and a cold trap are schematically represented. Inasmuch as the present invention is essentially concerned with the deposition of materials in very high vacuum environment, the diifusion pump and cold trap are known to be presented. However, it is well known to those skilled in the art that the conventional method of evacuating a bell jar or like vacuum chamber 20 is by means of an ordinary mechanical or so-called roughing pump, following which an oil diffusion pump or the like is used, which takes the advantage of adsorption of nitrogen, oxygen and like molecules by oil vapors, which may then be easily trapped and excluded by the diffusion pump.

The cold trap which is schematically shown normally consists of a ring surrounding the neck or junction between the diifusion pump and to the bell jar to prevent back flow of oil into the bell jar. The cold trap is maintained at an extremely low temperature by circulation therethrough of liquid nitrogen or other coolant. The operation of such roughing pumps, oil diffusion pumps and cold trap units are well known and conventional in the art of vacuum deposition and do not form any essential novel part of the present invention. All that is required is a ditfusion pump system or other like means which are capable of attaining vacuums of the desired order inside the chambers which are referred to in greater detail below.

Likewise, referring to FIGS. 1 and 4, there are shown a plurality of outlets 156 or the like, having covers or plugs 158 therein which are adapted to be vacuum sealed, but which are placed in the base 26 or the like of the vacuum chamber 20 for purposes of access to the interior of the chamber 20. In this manner, it is easy to introduce members such as the conduit 128 shown in FIG. 2, or to provide valve means for introducing the gases referred to in detail below.

Thus, FIG. 4 schematically shows a connector 160 leading to an inert source 162, and shows that regulator and needle valve means 164 may be provided to control the flow of gas from the source 162 to the interior of the vacuum chamber 20. These features are used with the present invention, but their particular structure forms no essential part of the invention, and thus no details of these units are shown.

Referring now to FIG. 6, there is shown a combination oscillator, amplifier, and impedance matching network unit 166.

FIG. 7 shows a power supply unit for some of the components of the combination unit 166, and FIG. 8 shows a power supply unit for some of the other components thereof.

Referring now to FIG. 6, and to the combination unit 166, there is shown a matching box or impedance matching network which includes leads 172 and 174, each of which terminates in plates 144. These are the plates across which the radio frequency voltage referred to elsewhere herein is impressed, that is, the electrode plates in the vacuum chamber. Tuning of the plates 144 is accomplished by adjusting the variable capacitors 176, 178 which extend across the leads 172, 174. A voltmeter unit 180 is center tapped at 182 to the secondary 184 of the matching box transformer 186. The primary 188 of the transformer 186 is connected to the secondary 190 of the output transformer 192. The primary of this transformer, in combination with a variable capacitor 196, forms an output tuned circuit which is connected through a coil 198 and a capacitor 200 to the output circuit of the amplifier portion 202 to the combination unit 166. A grounded capacitor 204 is connected between the coil 198 and the capacitor 200.

A high voltage connector 206 carries high voltage to a junction 208 between the output line 210 and a lead line 212, through two coils 214, 216, between which is disposed a filter capacitor 218. From the junction 220, the lead line 212 is connected to the plates 222, 224, respectively of the power tubes 226, 228. The plate cur rent flowing to the juction 220 and in line 212 passes through a coil 230 before being fed to the output transformer 192. Since power tubes 226, 228 are connected in parallel, it will be noted that screen grids 232, 234, are connected to a common screen grid input line 236.

From this drawing it also may be seen that the control grids 242, 244 of the power tubes are connected in parallel at the juction 240. The voltage at line 238 consists of DC bias and RF. drive. The bias is supplied at the connection 254 and is fed through an assembly 252 including a millammeter 258, the 3K w. resistor, the 1 mh. choke and the secondary 246 of the transformer 248 (L2). The RF. grid drive is developed across the secondary 246 of transformer 248, tuned to resonance by the capacitor 250. The 10 pf. variable capacitor is tuned to neutralize the plate to grid capacitance of the tubes 226, 228. It accomplishes this by providing a negative feedback path from the plate to grid circuit, thus eliminating self-oscillation of the output tubes. The 270 pf. capacitor and 1 mh. choke are part of the neutralization circuit. The 3K resistor is a grid resistor, providing a minimum bias level. The capacitors 256 are R.F. bypass capacitors.

Referring now to the oscillator portion 260 of the unit 166, it is shown that the circuit is a so-called Col'pitts type oscillator. The coil 262 and capacitor 264 are the major frequency determining components. The capacitor network 274 attached to the grid control 266 of the tube 268 for oscillation, the level of which is determined by their ratio. The choke coil connected to the cathode 272 provides the feedback voltage for the capacitive voltage divider 274. The resistor 270 is a grid leak bias resistor. The capacitor in parallel with it stabilizes the bias. The oscillator output is developed across the plate choke 282, capacitively coupled 'by capacitor 284 to the tuned primary 288 of the transformer 248 (L2). The primary is tuned to resonance by capacitor 286. The plate lead 276 is joined at 278 to the line 280, which connects to the B+ voltage source.

Thus, the output of the oscillator tube 268 is inductively coupled to the amplifier unit 202, and from the amplifier, the signal is fed to the matching box and supplied to the plates 144. As stated above, a preferred frequency of operation is about 13 megacycles per second, at a net power rating of about 600 watts or more.

Referring now to FIG. 7, there is shown a combination voltage control and rectifier unit for supplying regular power to the radio frequency amplifier just described. This voltage control and rectifier unit 290 comprises lead 292 for attachment to a 220 volt, 60 cycle single phase alternating current source. One lead 292 is directly connected to a primary winding 294 of a transformer 296, and the other lead is split at juction 298 between connections to one terminal of a semiconductor controlled rectifier (SCR) 300 biased in one direction, and other connection is joined to an oppositely biased SCR 302, the two SCRs being reverse parallel wired. A variable resistor voltage control unit 304 is connected in series between the terminal of the second SCR 302 and a junction 306, to which are connected a resistance-capacitance-resistance circuit 308 and a capacitor 310 in parallel. Take off lines 312 and 314 are fed respectively from the resistance-capacitance resistance circuit 308 to the gates 316, 318 of the SCRs 300, 302. At junction 320, the output from the cathode of SCR 302 and from the anode of SCR 300 are joined, and lead 322 connects this junction 320 to the primary 294 of the transformer 296-.

The secondary 324 of transformer 296 has the ends thereof respectively connected to a conventional diode rectifying bridge 326, of which one lead is grounded and the other fed to a high voltage source 328 through a choking coil 330. A fixed capacitor 332 cooperates with the choke 330 to stabilize or smooth the output of the rectifying bridge 326. Direct current dropping resistors 334 are provided so that a lower voltage may be fed 10 from terminal 336 to the screen grids of amplifier tubes 226, 228.

Referring now to FIG. 8, there is shown a power supply adapted to furnish B+ voltage to certain elements of the amplifier, oscillator and matching box unit 166, and to furnish heater current for tube filaments. This power supply 338 includes leads 340 for connection to a volt, 60 cycle single phase alternating current source, and these leads have a radio frequency filter system 342 disposed across them. A resistor 344 and neon tube 346 are also wired parallel to the leads 340, which connect to either end of a transformer primary 348, which is coupled through a core 350 to three separate secondaries. a B secondary 352, another secondary 354 having outlet leads marked A and B, and a third secondary 356 having outlet leads marked C and D.

The B+ secondary 352 has rectifier diodes 358, 360 attached to either end thereof, and a bias connector 362 as well as a center tapped and grounded parallel resistance-capacitance circuit 364 connected thereto. The output from the rectifying diodes 358, 360 is fed through choking coils 366, and is further stabilized or evened out by reason of the capacitor 368. The direct current from the B+ source is then fed through resistor 370 to a grounded resistance connector 372 and from there to a B+ outlet 374, which is also grounded through 2. capacitor 376.

The A and B secondary 354 is center tapped and grounded, and the low voltage output therefrom is used to heat the filaments of the tubes 226, 228. Similarly, secondary 356 contains a center tapped connection 378 which is grounded and connected to two capacitors 380 disposed across the output lines 382 leading to the heating element for the oscillator tube 268.

A group of samples was prepared as follows:

EXAMPLE 1 The apparatus shown in FIGS. 1 to 4 was used with a bell jar 20 comprising the outer vacuum chamber. A plurality of razor blades were carefully cleaned, as by immersing them in, and evaporating therefrom a solvent, such as trichloroethylene or other suitable solvent. The blades were placed on holding means, such as the bayonet unit shown at 84 in FIG. 5. Thereafter, a mechanical roughing pump was turned on, evacuating most of the air from the vacuum chamber 20. By means of an oil diffusion pump and cold trap, the pressure inside the air chamber 20 was further evacuated until a pressure of l l 0 millimeters of mercury was attained.

Thereafter, by means of a needle valve or like socalled leak valve, such as that schematically indicated at 164 in FIG. 4, argon gas was allowed to be introduced into the chamber 20 until the pressure was raised to 3 10- millimeters of mercury (Torr).

Thereupon, the radio frequency generating unit such as that shown in FIG. 6 was actuated, and a radio frequency of 13.56 megacycles was impressed on the plates 144, the matching network associated with the RF unit being adjusted or tuned so as to minimize the impedance caused by the target plates 152. Charging the plates with RF. current immediately causes a glow discharge to be produced between the plates. Thus, the electrons trapped between the plates 144 rush back and forth therebetween at a frequency of about thirteen million times per second, and many of these electrons strike the atoms of argon gas disposed between the plates. Because the argon is very massive in relation to the electrons, the argon atoms or molecules themself are not substantially moved solely by the movement of the electrons. However, the high frequency electrons bombarding the argon gas cause ionization thereof, and upon ionization, each positive ion of argon is strongly attracted, by reason of the high negative potential to one or the other of the plates 144. This potential accelerates the argon atoms toward the electrode 144 with great velocity. However, the ionized argon atoms strike the target material which is placed on the plate 144 or on the target plate 152 placed immediately in front of the electrode 144. The momentum with which the ionized argon atom strikes the target plate may be sufficient to sputter one atom or molecule of the target plate 152, as desired. Sufficient repetition of this action which occurs millions of times per second, causes a uniform deposition of coating material on the substrate.

When initial ionization takes place, the pressure inside the chamber 20 is reduced by reducing the rate of addition of argon, to 1.5 l mm. of mercury. Thereupon, the RF energy input is raised to a value of 600 watts forward power.

In this case, a DC bias of 1800 volts was built up on the electrode-target assembly relative to the glow discharge. The glow discharge carries itself substantially the same potential as the blade carriers. It is believed that this bias occurs because of the intrinsic characteristics of the circuit, that is, the electrode-target assembly appears to take on a strong negative charge; the bias is not separately applied to the assembly or the carrier. While the particles which are sputtered from the target plate are in a neutral state, that is, they are not ionized, and therefore are not attracted to the substrate or article to be coated by reason of the bias between the plates 144 and the article carrier, a certain degree of bias is desirable to prevent positively charged argon or like ions from striking the articles, since this would result in re-sputtering either the substrate or the coating sought to be applied.

Thus, the bias between the plates and the carrier is desirable, but its value is not of critical importance to the invention.

At this point, the amount of forward power in the system is then adjusted by altering the amount of argon introduced into the system by very minute adjustment. It is preferred that after arriving at a pressure of between 1 and 2 10 millimeters, and adjusting the impedance matching network, there will be about 500' to 600 watts forward power and about 100 watts or less of reflected power, leaving a net power input into the peak or to the two plates and the area therebetween of about 500 to 600' watts, and preferably about 510 to 550 watts.

Under these conditions, in one case, sputtering took place for a period of approximately four minutes, and a coating having thickness of about 625 angstroms (A.) was deposited upona fiat surface, and about half that thickness, namely 264 angstroms, was deposited on the edge portions of a razor blade, disposed with the razor edge portion thereof directed generally to the area between the peak.

The razor blades coated by the process just set forth were shown to possess an extremely fine, pore-free and uniform coating of chromium, rendering them resistant to rust and corrosion. Such blades, which possessed a very sharp or keen edge, also required no further honing or other treatment, and were ready from use when removed from the vacuum chamber.

Although the exact reasons for the success of the sputtering apparatus and method of the present invention are not entirely understood, it is believed that, because the coating material is liberated from the target plate in substantially atomic or molecular size particles, the adhesion thereof to the substrate or articles to be coated is very strong.

EXAMPLE 2 In this example, all the conditions were the same as those set forth in Example 1, the coated material was chromium, a plurality of blades were placed on the bayonet or carrying unit 84, and a plurality of these carrier units were inserted in the hub 64. Thereafter, the sputtering process was carried out in accordance with the conditions of Example 1, except that it was continued for a longer time and the entire carrier unit 28 was revolved through two complete cycles, thus exposing the top and bottom edges of the plurality of razor blades held in each bayonet unit 84 to the plasma peak or sputtering module 30 for the same length of time and at the same angle as all the other blades. The process was timed so that a coating of approximately 500 to 600 A. of chromium was deposited on the edge portion of each razor blade. In this example, the argon was continually admitted during the process, maintaining the operating pressure set forth in the first example and the sputtering took place continuously until each bayonet unit had made two passes beneath the sputtering module 30. This operation required 36 minutes, since the drum unit revolved twice, at a rate of 20 degrees per minute.

EXAMPLE 3 A method such as that referred to in Example 1 was carried out, with all conditions thereof remaining the same, except, that during the time the argon was leaked into the ball -jar, a small amount of oxygen gas allowed to enter the jar. By allowing sufiicient oxygen to enter the jar to react with the chromium, but not enough oxygen so as to substantially diminish the vacuum in the system or to interfere with the creation of the plasma, it was discovered that a coating of chromium oxide was able to be placed on the blades. Thus, this method demonstrates the ability of the method of the present invention simultaneously to carry out coating deposition and to allow a chemical reaction between the coating material and another product introduced into the vacuum chamber.

It is believed that, since the sputtered coating material is generally in a monoatomic or monomolecular form, the availability of individual atoms or molecules for reaction is great, and the probabilities of the desired reaction taking place are excellent. Thus, a principal advantage of this method is that it makes possible what is essentially a gas phase reaction at temperatures greatly below the vaporizing or sublimation temperatures of refractory materials, such as, for example, the types of metals referred to herein.

Although the reason is not clearly understood, it is known that coating such as those described herein may be applied to the cutting edges described, without joining the edges together. It is possible that, since the electrode plates are disposed at an angle relative to the faces which define the cutting edges of the blades or other instruments, that sputtered molecules do not fly vertically into the valley between any pair of blades in substantial numbers compared to the number striking the faces near the cutting edegs of the blades or the like.

It will thus be seen, that the present invention provides a novel method and apparatus for making the articles described herein, said method, apparatus and articles having a number of advantages and novel characteristics, including those referred to herein and others which are inherent in the invention.

We contemplate that numerous modifications of this invention may be made by those skilled in the art without departing from the spirit of the invention or the scope of the appended claims.

We claim:

1. A method of applying a thin coating film to the faces and cutting edge portions of a plurality of individual cutting instruments, each of which includes two honed relatively hard metal face portions with a narrow included angle therebetween, said faces meeting to define said cutting edge portion, said method comprising the steps of supporting said plurality of instruments on carrier means with said instruments having their sides abutting one another, and having said edges arranged in a common plane, disposing at least one electrode in the region of said instruments, disposing at least one target containing a metallic coating material thereon in a position such that said at least one target closely overlies said at least one electrode, positioning said carrier means such that said edges 13 are in an at least partially facing relation to said target, substantially evacuating the region surrounding said instruments, including the region surrounding said at least one electrode, impressing a voltage gradient between said electrode and a reference point sufficient to cause significant electron flow in the region adjacent said electrode, said voltage gradient being a radio frequency potential, introducing a minute amount of an inert gas into said evacuated area, whereby said flowing electrons ionize some of the molecules of said inert gas to form a plasma, and whereby the ions from said plasma strike the material disposed on said target, thereby sputtering said material from said target and onto said plurality of instruments, and discontinuing said process prior to deposition of about 500 angstroms of coating thickness on said edge portions.

2. A method as defined in claim ll wherein said instruments are razor blades and in which said method includes applying said coating film to both cutting edges of said individual razor blade where said blades are double edge blades, and comprising the further steps of repositioning said blades to coat the second edge thereof after the first edge has been coated, said repositioning being performed before opening said evacuated region to air.

3-. A method as defined in claim 2 which further includes providing a plurality of said carrier means, moving each of said carrier means beneath said opening in a timed relation, and rotating each of said carrier means one-half turn about its own axis and again moving each of said carrier means beneath said opening.

4. A method as defined in claim 1 in which said instruments are held at ground potential during sputtering.

5. A method as defined in claim 1 wherein said coating material is chromium and further comprising holding said carrier means in a position to receive sputtered chromium on said faces and said common-plane edges for the time required to sputter substantially 600 angstroms on a fiat surface positioned adjacent and parallel to said common plane.

6. A method as defined in claim 1 wherein said coating material is chromium and further comprising honing said faces until said edges have attained finished sharpness prior to sputtering chromium thereon, and sputtering onto said faces and said sharp edges snfficient chromium to form a continuous protective coating on said faces and edges and insufiicient to dull said edges.

7. A method as defined in claim 1 wherein said coating is deposited at a rate of at least about angstroms of coating thickness per minute of exposure of said edges to coating from said target.

8. A method as defined in claim 1 wherein said sputtering is carried out at a rate such that the coating thickness deposited on said edge is proportional to at least the product of about 10 angstroms times the number of minutes of sputtering exposure, and inversely proportional to the distance in inches between said edges and said target and wherein the pressure in said evacuated area is less than about one Torr.

9. A method as defined in claim 1 wherein said at least one electrode comprise two electrodes of substantial surface area, each electrode being relatively planar and disposed in at least partially oppositely facing relation to the other electrode, wherein said target is of approximately the same configuration as said electrode and is disposed in closely overlying relation thereto.

10. A method as defined in claim 1 wherein said at least one electrode comprises a pair of electrodes in the form of generally fiat plates, said electrodes being disposed in a relation such that the respective bottom edges are farther spaced apart than said top edges, whereby a peak is defined at the top of said pair of electrode plates and an opening is defined at the bottom thereof, and wherein said articles are disposed such that, during coating thereof, said edges are disposed in facing relation to said opening opposite said peak.

11. A method of increasing the durability in use of at least the sharpened edge portion of at least one hard metal cutting instrument, said method including disposing said instrument with said cutting edge thereon in an evacuable region, providing at least one electrode within said region, disposing target means in an at least partially overlying relation to said electrode, said target means including a layer of a coating material thereon selected from the class consisting of relatively hard, corrosion resistant metals and alloys, evacuating said region to an extremely high vacuum level, impressing a radio frequency alternating voltage on said electrode, thereby causing rapid electron flow in the area adjacent said electrode, introducing a minute amount of a normally inert gas into said evacuated area, thereby causing said flowing electrons to strike and ionize molecules of said normally inert gas, said ionized gas molecules being thereby attracted to and striking said target to sputter coating mtaerial therefrom, and collecting the coating material thereby sputtered from said targets on the cutting edge portion of said at least one cutting instrument in a thickness of about 200 angstroms or less, whereby the durability of said cutting edge is greatly increased without sen sibly decreasing the initial sharpness of said cutting edge.

12. A method as defined in claim 11 wherein application of said radio frequency alternating voltage is sufficient to desorb gases and organic contaminants from the surface of said cutting edge prior to application thereon of said coating to increase the strength of bond between said cutting edge and said deposited coating material.

13. A method of applying a thin coating film to the faces and cutting edge portions of a plurality of individual cutting instruments, each of which includes two honed relatively hard metal face portions with a narrow included angle therebetween, said faces meeting to define said cutting edge portion, said method comprising the steps of supporting said plurality of instruments on carrier means with said instruments having their sides abutting one an other, and having said edges arranged in a common plane, disposing a pair of electrode plates in such a relation that the respective top and bottom edges of said plate are parallel to each other and in which the bottom edges are farther spaced apart than said top edges, whereby a peak is defined at the top of said pair of electrode plates and an opening is defined at the bottom thereof, disposing tWo target plates containing a metallic chromium coating material thereon in a relation so that each plate closely overlies one of said electrode plates, positioning said carrier means beneath said opening at the bottom of the electrode plates with said cutting edges facing said opening, evacuating substantially all the air from the region surrounding said instruments and between said electrode plates, impressing a radio frequency alternating voltage across said electrode plates, thereby causing rapid electron fiow in the space between said plates, introducing a minute amount of argon gas into said evacuated area, whereby said flowing electrons ionize the molecules of said gas to form a plasma and the ions from said plasma strike the chromium disposed on said target plates, thereby sputtering the chromium from said target plates and onto said plurality of instruments.

References Cited UNITED STATES PATENTS 3,283,117 11/1966 Holmes 2l976 3,480,483 11/1969 Wilkinson 148-63 FOREIGN PATENTS 457,378 6/1949 Canada 204--192 1,428,243 1/1966 France 204192 OTHER REFERENCES E. M. Michalak: Pergamon Press Ltd., Great Britain, vol. 17, No. 6, March 1967, pp. 317324.

JOHN H. MACK, Primary Examiner S. S. KANTER, Assistant Examiner 

